DESCRIPTION: In the past several years the PI's laboratory has extensively characterized the tissue interactions responsible for induction of the embryonic lens, and this has led him to define four major stages in the lens determination process: competence, bias, specification and differentiation. Each of these stages can now be monitored by biological assays he has developed. At the same time, he, and others, have characterized a number of genes encoding transcription factors that either have been shown to be involved in eye determination or are likely candidates for such a function. New technological breakthroughs, e.g., a useful procedure for transgenesis in Xenopus, now permit a number of strategies for evaluating gene function. Utilizing this information about the biology and molecular genetics of lens determination, and new technical advances, he proposes a series of experiments to test the function of putative regulatory genes in lens determination in mouse and Xenopus embryos. The first goal is to examine promoter regulation of Xenopus crystallin genes. The second goal is to clone and characterize expression of members of two newly discovered gene families likely to be important in lens determination. The third goal is to define further the genetic hierarchy controlling eye determination by using mouse mutants and genetic interference experiments in Xenopus to assess genetic interactions. The final goal is to test the function of transcriptional regulatory genes in controlling lens competence, bias and specification in Xenopus embryos.